Patch is due on Tuesday, and comes on the heels of a separate Flash Player patch affecting both Reader and Acrobat

Just weeks after patching a critical flaw, Adobe Systems is rushing out another patch for its Reader and Acrobat software. The company also patched a critical issue in Flash Player Thursday.

The Flash Player flaw could be used by an attacker to trick a Web browser into doing things that it shouldn't, but it's not what is known as a remote-code execution flaw. This means it can't be used to directly install unauthorized software on a victim's computer, said Brad Arkin, Adobe's director of product security and privacy.

If the bug is exploited, "the attacker would be able to execute a general class of cross-site request forgery type of attacks," Arkin said. Adobe rates the issue as "critical."

Normally Adobe patches Reader and Acrobat in quarterly security updates, but Adobe is being forced to rush out next Tuesday's fix because these products are also susceptible to the Flash Player flaw, Arkin said. "We decided that we wanted to get the update for Flash Player out to users as soon as possible," he said. "We didn't want to wait any extra time to do a coordinated release."

In theory, hackers could learn about the bug by looking at the Flash Player patch and then use that information to attack Reader and Acrobat, but Adobe is giving them just a five-day window to complete this work. At present, Adobe isn't aware of any attacks that exploit this Flash Player bug, Arkin said.

Users who are worried about the Flash Player bug being exploited in Reader can reduce the threat by opening documents outside of the browser, Arkin said.

Next week's Reader and Acrobat update will also patch another undisclosed issue in the PDF-reading software, he added. The flaws affect Windows, Mac, and Unix platforms.

Adobe's security has come under scrutiny over the past year as attackers have increasingly leveraged Reader and Acrobat flaws to hack into computers. Because Reader is installed on almost all desktop computers, a well-crafted Reader attack can affect more victims than one that targets Internet Explorer or Firefox.

Adobe's next scheduled Reader and Acrobat update is due April 13.

Also on Thursday, Adobe patched an "important" bug in its open-source BlazeDS messaging software.